Frenchie dealing with non-metric screws on an old Claud Butl

[retromarin]

Hello guys,

I'm quite new on this discussion board and I hope i'm posting in the correct section
I'm also quite new in the world of restoring old moutain bikes
And last but not least, I'm totally new to the non-metric system that's used in england :cry: (frenchie inside...)

I have started restoring an old Claud Butler MTB (Spectre from 1994). It will progressively be transformed and used as a touring bike.

Unfortunately, I am faced with a problem when mounting racks and fenders on my frame. The M5 bolts just won't fit where they're supposed. M4 bolts are too small. I guess the Claud Butler was made with some other standard.

The inner diameter of the threaded hole is 4.2mm. I have looked into the UNC standard, but can't find a common screw that would fit this.

Then I thought that you guys may just have the answer before I buy all types of screws just to try them on my bike and hope they'll fit. Any suggestions on what I should try first ?

Cheers !
Rob

 

[BoyBurning]

Would be surprised if they aren't metric. Have you checked thread pitch?

BB

 

[legrandefromage]

I am currently working on a Butler from 1995 and all my usual bolts fit perfectly as they should?

My 1991 Spectre had pretty standard bolts too.

 

[retromarin]

Boyburning : on the thread : I actually have no idea how to check this as the thread I'd need to measure are internal... :?

Legrandefromage : thanks for the information, now i'm left wondering what I'm doing wrong... I just bought the rack new and the screw won't fit. Screws from another rack are a no-go too.

Mystery...

 

[legrandefromage]

Check for paint inside the holes but beyond that, ...?

 

[dyna-ti]

Something you should know about screw and bolt threads
http://en.wikipedia.org/wiki/Screw_thread

 

[Rampage]

4.2mm sound about right for M5.
Are you sure they arn't corroded, damaged or full of paint?

 

[retromarin]

I'm sure the screw I use M5 as it fits perfectly in the front fork.

I just tried harder on the screw : broke the (cheap) allen key that came with the racks Will try with my real allen key tonight !

Even if the allen key is dead, you guys may be right. Looks like there is some transparent coating on the threads... I'll email the seller to ask if he tried to do anything !

EDIT: if this is the explanation, I guess I'll have to make excuses on blaming some hypothetic non-metric system :roll: (not really sure this sentence actually means anything in english though...)

 

[legrandefromage]

I'm sure the screw I use M5 as it fits perfectly in the front fork.

I just tried harder on the screw : broke the (cheap) allen key that came with the racks Will try with my real allen key tonight !

Even if the allen key is dead, you guys may be right. Looks like there is some transparent coating on the threads... I'll email the seller to ask if he tried to do anything !

EDIT: if this is the explanation, I guess I'll have to make excuses on blaming some hypothetic non-metric system :roll: (not really sure this sentence actually means anything in english though...)

The bolts should also fit in the bottle cage mounts perfectly...?

 

[retromarin]

I'm sure the screw I use M5 as it fits perfectly in the front fork.

I just tried harder on the screw : broke the (cheap) allen key that came with the racks Will try with my real allen key tonight !

Even if the allen key is dead, you guys may be right. Looks like there is some transparent coating on the threads... I'll email the seller to ask if he tried to do anything !

EDIT: if this is the explanation, I guess I'll have to make excuses on blaming some hypothetic non-metric system :roll: (not really sure this sentence actually means anything in english though...)

The bolts should also fit in the bottle cage mounts perfectly...?

They do